If the cores were rinsed with a gentle stream of water...the roots appeared to be no more than 1 inch deep. If the cores were shaken gently by hitting the soil probe on the left fist...same result.
If the core was simply tipped over onto concrete, the cores remained mostly intact, but the sparse roots, if any were visible at all, were very tiny and thin. They were fine as hair.

I am not sure if this is a suitable method to measure root depth--or--if roots are just very shallow a this time of year. The same method was used to core a clump of tall fescue--with the same result.

This past couple weeks have been brutal,,, especially in sand where direct sun is involved... After Aug. 15th we should start to see the root growth again...
At least you have good moisture at that depth...

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Now that I know that clay's texture(platelets) has nothing to do with water infiltration, percolation, or drainage,,, I wonder what does...
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Thank you Riggle,
IF this post isn't helpful to most, It is helpful to me.
A couple months ago, we laid 80 yds + a little of fescue blend sod to a parcel of lawn that is mostly rock, some silt and 65% shade. We applied 5 1/2 cu.yds. topsoil to the rocky area for a root bed. The area is 30X30.
Fertilizer was not used at the time of installation. A couple weeks after the sod became webbed into the soil, things were well........deep green color,etc. The heat poured on and the color faded fast. Two weeks later, the company that fertilizes this lawn applied 46/0/0 to this blended bermuda / zoysia lawn and evidently the urea got a hold of the fescue. You can imagine that a root probe is useless in this case of rock at such a shallow depth. In my case, the roots don't extend any deeper than at least one inch. If it weren't for the irrigation, this sod would have perished anyway.

Did that get you about 2" of top soil as a base Think Green? Man, I am sorry about the urea mishap. Sounds like a difficult site long term.

Good pictures, Riggle. Scary how much things have shrunk up. I just took on a football field that is well over 50% weeds, is mowed way too short, and has not had any fertilizer, weed control, aeration, etc. for 7-8 years. It is a rich soil but compaction is surprisingly not a problem (not a big one anyway). Anyway, I pulled some plugs at the end of June for a soil test and cut some larger holes with a cup-setter to have a look under the hood. Rooting was fairly good then but has shrunk up considerably in the last 3 weeks.

Somewhere (Sports Filed Forum probably) I posted some root mass photos from seed trials I ran a couple years ago. It is apples to oranges as I was looking for which blend had the best roots and it was late September or October from a late August or early September planting.

foreplease,
has anyone considered the use of hydretain? I am curious as to the bottom line of holding in water at the root system during drought conditions.
The science has to be conducted for all turf grass types unless it already has.

Hmm...I would like to know too. Never heard of it until your post above. I Googled it and wastched a short video on it. It looks good but it is a sales video after all.

I have used wetting agents quite a few time. I would like to know how thus product works different from a wetting agent. I have several big area where I could conduct a good test. Maybe I will if we do not get any opinions here. Thanks for pointing it out.

Today I got some root cores of a nearby Bermuda grass lawn. Yes, we have a few spots of it in Michigan. I found a similar situation. There dense roots were about 2 inches deep, there were a few very fine roots up to about 4 inches deep, but...many times the cores just fell apart, as the roots were sparse and very thin.
I am not sure if this is a good method to determine the rooting depth. Temperatures were above 90 most of last week. We have had occasional showers.